The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Power tools often have electric motors that provide the motive power for the power tool. In a number of such power tools, a fan affixed to a shaft of the electric motor provides cooling air flow to the electric motor, and as applicable, to other components of the power tool.
One common type of motor used in power tools is a universal motor. With reference to FIG. 1, a universal motor 100 has a stator 102 and an armature 104 having a shaft 106. Stator 102 includes lamination stack 108 having field coils 110 would in slots (not shown) in lamination stack 108, such as slots around pole pieces 112 of lamination stack 108. A commutator 114 is affixed to a portion of armature shaft 106 extending from one side of lamination stack 108 of stator 102 and a fan 116 is affixed to a portion of armature shaft 106 extending from an opposite side of lamination stack 108. A fan baffle 118 is disposed around fan 116. Armature 104 includes coils 300 (FIG. 3) wound in slots 302 in a lamination stack 304 affixed to armature shaft 106. Ends of the armature coils are connected to segments of the commutator 114. Motor 100 includes a field case or housing 120 in which stator 102 and armature 104 are disposed. Fan baffle 118 is illustratively affixed to housing 120. Opposed ends of armature shaft 106 are disposed in bearings 122, only one of which is shown in FIG. 1.
Each field coil 110 has opposed axial ends 124 extending axially outwardly from opposed axial ends 126 of lamination stack 108 of stator 102. Each field coil 110 illustratively has an arcuate cross-section and opposite circumferential sides of the field coils at each axial end 124 the field coil taper radially outwardly. As such, there are gaps 128 between the circumferential sides of the field coils 110 at opposed axial ends 124 of the field coils. Gaps 128 are generally V-shaped. In motor 100 shown in FIGS. 1 and 2, there are two field coils 110 and there two V-shaped gaps 128 on opposed sides of motor 100 adjacent one axial end 126 of lamination stack 108 and two V-shaped gaps 128 on opposed sides of motor 100 adjacent the other axial end 126 of lamination stack 108.
With reference to FIG. 3, there are two general passages through which air can pass through motor 100. These are passage 306 between the inside of stator 102 and the outside of armature 104 and passage 308 between the outside of stator 102 and the inside of field case or motor housing 120.
As mentioned, motor 100 may illustratively be used in power tools. By way of example and not of limitation, motor 100 may illustratively be used in a band saw 400 shown in FIG. 4, which is illustratively a DeWALT® Heavy-Duty Deep Cut Variable Speed Band Saw, model D28770, manufactured by Black & Decker, Inc. of Towson, Md. Bandsaw 400 includes a first or front section 402 and a second or rear section 404, which can be joined together by a center section 407 in which a motor, such as motor 100, is disposed. Motor 100 is coupled via an output shaft to a saw blade system 406 having a saw blade 408 entrained on wheels (not shown) in front and rear sections 402, 404. Motor 100 drives saw blade system 406.